In an automotive vehicle, it is known that a seat belt harness includes webbing and a buckle that latches the webbing across an occupant to restrain and protect an occupant from injury during a collision event. The seat belt harness is often additionally used as part of an occupant detection system that further protects vehicle occupants in the event of a vehicle crash. One type of passenger occupant detection system includes a belt tension sensor (BTS). Current belt tension sensors are constructed as part of a seat belt harness assembly to measure cinch tension applied axially along the webbing of the seat belt harness, yet still allow the restraint function to be performed. The belt tension sensor data is especially important to categorize a tightly cinched child seat belted into the front passenger seat. The pressure sensor and belt tension sensor components of the passenger occupant detection system electrically connect with a controller. The cinch tension data from the belt tension sensor and the pressure sensor data produced by the pressure sensor are input to the controller. The controller analyzes the cinch tension data in an algorithm that compensates the pressure sensor data for the additional load produced by the cinched seat belt harness represented by the cinch tension data. The compensated pressure sensor data is a more precise reading of the actual weight in the passenger seat that is used by the passenger occupant detection system to determine a deployment decision to deploy or not deploy a passenger vehicle air bag. The passenger occupant detection system communicates the deployment decision output to the vehicle's air bag controller or sensing diagnostic module (SDM) that implements the passenger occupant detection system's air bag deployment decision if a vehicle collision event occurs.
One current belt tension sensor device comprises a housing that further contains springs, magnets, and a Hall Effect sensor that increases device cost. A second current belt tension sensor design includes a hub, disc portion, and rim components that also increase device cost. Further, current belt tension sensor devices have a disadvantage of being large and connect between the seat belt harness and the frame of the vehicle adding bulk, complexity, and expense to the seat belt harness assembly.
Therefore, what is needed is a robust seat belt assembly for reliably sensing tension on the webbing, eliminates the need to perform the restraint function for the occupant on the seat belt harness, is attached on the webbing of the seat belt, has a lower material and serviceability cost, has a lower component weight, and is easily integrated into the webbing of the seat belt harness.